What you said it correct, and what the other user said Is correct too, so, let's just say that the both of you are correct, VPN actually does more internally than we all can actually see or take notice of.
Technically spea,what NotATether said is correct. Using a VPN doesn’t increase Internet/download speed but it does help you bypass ISP resrictions/limits,
aka throttling. If you have a 5mbs internet speed, a VPN cn’t turn it into 100 mbs.
But however, one question I want to ask is, is it possible for someone to connect his or her VPN to the same network in a country where he or she resides? Like for example, I live in Nigeria, and I want use VPN to visit a site, is it possible to connect my VPN network to Nigeria? Will there be any difference if it's possible to do?
Yes you can. There is no problem in connecting to a local VPN server, if available.
The only problem is that this won’t help you bypass georestrctions.
However, it will help to hide your location within your own country.
Although I am not sure that this is a really reliable means of maintaining anonymity (as well as all VPN protocols), but from a mass and inexperienced in network routing algorithms user, who is not specifically engaged in some kind of location search, it should help. And this can also sometimes be useful simply for the purpose of maintaining anonymity in some specific case.
Of course, I am talking about the possibility of some completely legal actions on the part of the user. For example, it helps you hide where you are from your girlfriend for some personal reasons.